(a). Field of the Invention
The present invention relates in general to the field of gain control, and more particularly to a system and method that adjusts the gain value according the signal strength and background noise informations retrieved from received radio frequency (RF) signals, thereby optimizing received RF signal quality.
(b). Description of the Prior Arts
In the Internet era, people tend to consume a lot of information rapidly. Personal mobile products, such as cellular phones and personal digital assistants (PDA), encourage this trend and are popularized to daily life with the progress of wireless communication technologies.
The personal mobile products achieve the goal of making communications any time and any place by means of the wireless communication technologies, which abandon wire connections used by wire communication. FIG. 1 is a block diagram showing a conventional wireless communication architecture, which includes a receiving unit 1, a processing unit 2, a transmitting unit 3, and an antenna 4. The receiving unit 1 receives a wireless signal 10 via the antenna 4. The processing unit 2, coupled to the receiving unit 1, processes the wireless signal 10 in a proper manner, such as high frequency noise elimination, quantization, etc., to transfer into the user data formats. On the other hand, the processing unit 2 receives signals in the user data formats and transfers them into a proper format suitable for the transmitting unit 3. The transmitting unit 3 amplifies the signals from the processing unit 2, and transmits them out via the antenna 4.
However, the quality of the wireless communication is deeply subject to many distortion elements in the surrounding environment, such as space attenuation, loss, reflection, rotation, added noise, interference, etc., thus the receiving unit 1 adjusts its gain value according to the signal strength of received signals, thereby maintaining the received signal quality. Here the gain value is the ratio of the output power to the input power of the receiving unit 1, and it implies the signal amplification ability of the receiving unit 1. However, when the received signals are amplified by the receiving unit 1, background noises are also amplified. Accordingly, it is hard to improve the received signal quality during the signal amplification, and this is very disadvantageous for the subsequent signal demodulation and identification. Therefore, what is needed is a system and method for RF gain control that can keep the noises in a low and constant level and thus improve the received signal quality.